[chuckm]

CAI is good when you've got the pedal smashed and the throttle plate is wide open. In those situations, most cars tend to run rich simply because it the engine is starving for air. Since cold air is more dense, it reduces this problem slightly. At part throttle, a CAI is largely neutral and perhaps a slight negative. The engine isn't starving for air and cold air is more viscous, translating into greater pumping losses.
I've never really looked into the whole exhaust side of the equation.